May’s chief of staff, Nick Timothy, said that MI5 believes Chinese intelligence services are working “against British interests at home and abroad.”

In his 2013 memoir Power Trip, Brown’s former adviser and “spin doctor” Damien McBride described the 2008 “honey trap” incident.

Brown’s team was “accosted on one side by a beautiful posse of Chinese girls and on the other side by an equivalent group of Russian blondes,” McBride wrote.

Even before our resident security expert could warn us that their interest was not to be taken at face value, we looked up and saw one of our number disappearing up the stairs to the exit with one of the girls, beaming back at us.”

He woke up the following morning “minus his Blackberry and half the contents of his briefcase”.

The official also had a “very bad headache, owning to the Mickey Finn nightcap his overnight companion had administered to him in his hotel room,” McBride wrote.

A source told the London Telegraph that security chiefs warned May’s staff that hotel rooms used during the summit were likely to be bugged. “We have been told that if you feel uncomfortable about people seeing you naked, you should get changed under your bedclothes,” the source said.

In 2008, a British official was reported to have had his mobile phone and secret documents stolen after he was seduced.

Officials traveling with May have been issued temporary mobile phones and email addresses in an attempt to evade the “honey traps” and Chinese state hackers.

May’s staff were also warned against keeping gifts they receive at the summit and to be particularly wary of electronic devices, such as free computer memory sticks, mobile phone SIM cards or chargers offered by their Chinese hosts.